Concert Pharmaceuticals Inc. shares dropped 9.7% to $14.50 Wednesday morning after the Food and Drug Administration put its hair loss drug on clinical hold. The regulator imposed the hold before subjects in the phase 2a trial were dosed, and said that it needed to review certain toxicology studies to support the one-year dosing planned for the trial. "The FDA did not cite a safety concern," said Concert Pharma. The company plans to submit the requested reports soon, after which the FDA has 30 days to tell Concert Pharma whether it will lift the clinical hold. The drug in question, CTP-543, is intended for the autoimmune skin disease alopecia areata, which causes hair loss typically on the scalp and face, and affects nearly 7 million people in the U.S., according to the National Alopecia Areata Foundation. Concert Pharma shares have risen 44.1% over the last three months, compared with a 1.4% rise in the S&P 500 .